1. Field of the Invention
The invention relates to an electrochemical measuring device for determining the oxygen content in gases with approximately constant pressure, especially in combustion exhaust gases, with an oxygen ion-conducting solid electrolyte which is provided with at least two electrodes, of which at least a first electrode can be exposed to a sufficient degree to a constant gas stream provided for the measurement and both electrodes can be connected to a voltage source, a current measuring device being inserted into the circuit, and to the use of such measuring device for controlling the fuel-air ratio of a burner for fluid fuels.
2. Description of the Prior Art
In one known measuring device of this type, an electric d-c voltage is applied to the electrodes and the first electrode, acting as a cathode, is exposed to the gas stream to be measured. This extracts the oxygen component of the gas stream electrolytically from the gas stream. This oxygen component is then transported in the form of oxygen ions through the solid electrolyte to the second electrode and is oxidized there to oxygen molecules. The current which then flows and is measured by the current measuring device is a measure for the oxygen ion transport and thus for the oxygen content of the gas stream.
However, in order to be able to give quantitative information regarding the oxygen content, it is necessary to extract all the oxygen from the gas stream, to measure, if necessary, the magnitude of the gas stream, and to hold the gas stream constant during the measurement. While the first requirement can be met by sufficient size of the electrodes and the second requirement in a simple manner by a calibration, the third requirement, namely, holding the gas stream constant, is usually difficult and can be met only with a large expenditure of technical means.